[AGENT++] VACM 3.5.13 problem

[Marek Malowidzki]

While we did not explain the problem completely, there is some new info.

> Not quite. Scalars are accessed using GET while tables are retrieved with
> GET-BULK. It looks like it really hangs, i.e. it is impossible to read
> anything else (GET, GETBULK, both do not work anymore). I seem that both
> SNMPv1 and v3 are blocked but we will make sure on Monday.

In fact, the agent does not block. Simply, our embedded hardware is so slow
that it remains blocked for about 1 minute or longer while we make GETBULK
requests to non-available (due to VACM masks) subtrees. Looks like there is
significant overhead related to access checks. On faster hardware, the delay
is almost unnoticeable.

However, in a situation when we remove access to a given subtree but grant
access to some variables that are "after" this subtree, snmpwalk tool from
NET-SNMP package reports "no such object" error, which seems to be
incorrect. When nothing is accessible to the end of the whole MIB, the
correct "end of MIB view" is returned.

We observed the same behavior under 3.5.13 and 3.5.14. We will try to
collect logs on Monday.

Merry Christmas!

Marek